Plasma is an ionized medium that contains many active components including electrons and ions, free radicals, reactive molecules (e.g., ozone, nitric oxide (NO), etc.), and photons. Plasma treatment has been used in materials processing for years to provide desired surface characteristics on plastics, paper, textiles, semiconductor materials and others. The demonstration of atmospheric plasma processes has broadened the field to include treatment of materials that are unsuitable for vacuum processes.
Plasmas are generally categorized as either hot (thermal) or cold (non-thermal) plasma. In a hot plasma, the electrons and heavy particles are in equilibrium with one another and the environment and the temperature of the heavy particles is about equal to that of the electrons. In a cold plasma, the cooling of the heavy particles is more efficient than is the energy flux from the electrons to the heavy particles and the overall temperature of the plasma can remain much cooler than the electron temperature.
Moreover, plasmas can be utilized in either a direct or indirect mode in order to contact a surface to be treated. In the direct mode, the plasma jet itself, which includes the ignited charged and uncharged species, contacts the treated surface, and a significant flux of charge reaches the treatment area. In an indirect plasma treatment, the treatment jet is the downstream afterglow of the ignited plasma plume in which some of the plasma species have become de-excited and have recombined. In an indirect mode, the contacting plasma stream includes mostly uncharged atoms and molecules, with relatively little charge reaching the treatment surface. Although both modes of operation have been shown to be effective, the direct mode can be highly effective in much shorter treatment times.
While atmospheric pressure plasma jet (APPJ) devices, which include a tube with carrier gases and electrodes, have been developed to create non-thermal atmospheric pressure plasmas, such devices are based upon weakly ionized discharge and their emitting intensities are relatively low in comparison to low pressure plasmas created using vacuum chambers.
While the above describes improvement in the art, room for further improvement exists. What is needed in the art is an atmospheric pressure plasma jet device that can exhibit an increased optical intensity and that can be used in applications requiring high energetic plasmas.